1. Technical Field
The present disclosure relates in general to wireless communication devices and in particular to antenna arrangements in wireless communication devices.
2. Description of the Related Art
With the rapid deployment of Long Term Evolution (LTE) Fourth Generation (4G) networks, an increasing number of wireless communication providers are implementing Simultaneous Voice and LTE (SVLTE) data technologies. For example, voice communication within SVLTE is supported using Third Generation and/or Code Division Multiple Access (CDMA) technologies and data communication is provided using 4G technologies, which can be supported in more recently designed smart-phones.
While providing SVLTE communication (e.g., by using LTE Band 13 and the CDMA850 band), wireless communication devices can experience high levels of desensitization of receivers in select channels of CDMA850 and LTE Band 13. These high levels of receiver desensitization present a serious challenge to designers of wireless communication devices. Furthermore, designers are challenged to provide acceptable levels of LTE multiple input multiple output (MIMO) performance by utilizing LTE receive antennas that are not correlated. In order to mitigate SVLTE desensitization, some conventional approaches utilize highly linear and large sized ceramic filters or a number of smaller filters in the front end, as well as high third order intercept point (IP3) PIN switches. The large filter or even the smaller filters cannot be packed in a thin phone design. Furthermore, the antenna bandwidth requirement to cover a wide low band requires a relatively large ground clearance distance, which requires a greater phone Y dimension (i.e., length).
Another approach employs (a) a separate 3G (CDMA) and LTE transmit antenna to realize antenna isolation of at least 10 dB and (b) small size notch filters on the front end. For example, a separate CDMA main antenna is positioned on the bottom of the device and a separate LTE antenna at the top of the device for signal transmission (Tx) only or for both signal transmission and reception (Tx/Rx). However, having a transmit antenna at the top of the phone results in higher Specific Absorption Rate (SAR) and poor “Phantom” Performance. SAR compliance is generally challenging with multiple antenna/transmitters in phones. In a thin phone, the SAR performance and Phantom performance that is used to measure detuning impact are both reduced when a transmit antenna is positioned at the top of the wireless communication device. Generally, a thin phone has a substantially uniform thickness of less than 10 mm or a “bump” segment at the top of the device, which bump segment generally has a thickness that is greater than 10 mm.
In other approaches, separate 3G (CDMA) antenna and LTE antennas at the four corners of the phones (either combined diagonally or individually excited) are utilized. In this case, each antenna element has its own antenna volume spread partially around the bottom/top edges and the side edges. Having a transmit antenna at the top or upper side (even if combined with a bottom antenna element) still has significant SAR issues in a thin phone. Also, Phantom performance is worse when the antenna is placed at the top or the side of the device than when the antenna is positioned at the bottom of the device. Having the antenna elements positioned on the sides makes the X dimension (i.e., width) of the product significantly wider than the display width requires. A tighter X dimension of the phone becomes critical to comfortably holding the phone when a bigger display size is used. A wider X dimension makes the border around the display larger. Furthermore, having portions of the main antenna elements on the bottom sides of the phones make the antenna elements more susceptible to significant hand detuning/loading “variation” effects in natural hand holding talk positions than having antenna elements entirely confined to the bottom.